1. Field of the Invention
The present invention relates to a communication control apparatus and method, a communication system, and a program storage medium. In particular, the invention relates to a communication control apparatus and method, a communication system, and a program storage medium which make it possible to reliably control a connection between devices via a plurality of networks.
2. Description of the Related Art
In a system in which data on an IEEE (Institute of Electrical and Electronics Engineers) 1394 serial bus is transferred via an ATM (asynchronous transfer mode) network, to enable exchange of data between digital AV (audio-visual) devices connected to the ATM network, it is necessary to establish a data flowing connection in advance. The present assignee proposed a method for establishing such a connection, as Japanese Patent Application No. Hei. 11-147781 (corresponding to PCT Application No. JP 99/02864 and U.S. patent application Ser. No. 09/463,333), for example.
FIG. 1 shows an example configuration of this network system. As shown in FIG. 1, an ATM/1394 bridge 4-1-1 is connected to a personal computer 1-1-1 via an IEEE 1394 serial bus 2-1 and also connected to an ATM network 5 via a UNI (user-network interface). Video data that is transmitted from a digital video camera (DVCAM) 3-1 through the IEEE 1394 serial bus 2-1 is transferred to the ATM network 5. An ATM/1394 bridge 4-2-1 is connected to a personal computer 1-2-1 via an IEEE 1394 serial bus 7-1 and also connected to the ATM network 5 via a UNI. Video data that is transmitted from the digital video camera 3-1 over the ATM network 5 is transferred to the IEEE 1394 serial bus 7-1.
Connected to the digital video camera 3-1 via the IEEE 1394 serial bus 2-1, the personal computer 1-1-1 transfers, to the ATM/1394 bridge 4-1-1, through the IEEE 1394 serial bus 2-1, video data that is transmitted from the video camera 3-1 through the IEEE 1394 serial bus 2-1. That is, the digital video camera 3-1, the personal computer 1-1-1, and the ATM/1394 bridge 4-1-1 are connected to the same IEEE 1394 serial bus 2-1.
Connected to the ATM/1394 bridge 4-2-1 via the IEEE 1394 serial bus 7-1, the personal computer 1-2-1 transfers, to a digital video cassette recorder (DVCR) 8-1, through the IEEE 1394 serial bus 7-1, video data that is transmitted from the digital video camera 3-1 through the IEEE 1394 serial bus 7-1. The ATM/1394 bridge 4-2-1, the personal computer 1-2-1, and the digital video cassette recorder 8-1 are connected to the same IEEE 1394 serial bus 7-1.
To simplify the description, the above description has been made in such a manner that data is transferred from one sub-network system on the left side of the ATM network 5 to another sub-network system on the right side of the ATM network 5. However, in the example of FIG. 1, m sub-network systems are provided on the left side of the ATM network 5 and n sub-network systems are provided on the right side of the ATM network 5. Actually, data can be transferred from an arbitrary sub-network system among those sub-network systems to another arbitrary sub-network system.
When communication is performed between the personal computers 1-1-1 and 1-2-1, C (control)-plane protocol stacks are laid out as shown in FIG. 2.
As shown in FIG. 2, the C-plane protocol stack of the personal computer 1-1-1 is constituted of a 1394 PHY layer 11-1, a 1394 link layer 11-2, an ASEL layer 11-3, an SSCF (ITU-T Q.2130)+SSCOP (ITU-T Q.2110) layer 11-4, and a Q.2931 (ITU-T Q.2931) layer 11-5. The personal computer 1-1-1 side of the C-plane protocol stack of the ATM/1394 bridge 4-1-1 is constituted of a 1394 PHY layer 12-1, a 1394 link layer 12-2, an ASEL layer 12-3, an SSCF+SSCOP layer 12-4, and a Q.2931 layer 12-5. On the other hand, the ATM network 5 side is constituted of a PHY layer 13-1, an ATM layer 13-2, an AAL5 layer 13-3, the SSCF+SSCOP layer 12-4, and the Q.2931 layer 12-5.
The C-plane protocol stack of the ATM network 5 is constituted of a PHY layer 14-1, an ATM layer 14-2, an AAL5 layer 14-3, an SSCF+SSCOP layer 14-4, and a Q.2931 layer 14-5.
The ATM network 5 side of the C-plane protocol stack of the ATM/1394 bridge 4-2-1 is constituted of a PHY layer 15-1, an ATM layer 15-2, an AAL5 layer 15-3, an SSCF+SSCOP layer 15-4, and a Q.2931 layer 15-5. On the other hand, the personal computer 1-2-1 side is constituted of a 1394 PHY layer 16-1, a 1394 link layer 16-2, an ASEL layer 16-3, the SSCF+SSCOP layer 15-4, and the Q.2931 layer 15-5.
The C-plane protocol stack of the personal computer 1-2-1 is constituted of a 1394 PHY layer 17-1, a 1394 link layer 17-2, an ASEL layer 17-3, an SSCF+SSCOP layer 17-4, and a Q.2931 layer 17-5.
The ASEL layers 11-3 and 12-3 allow application of a signaling protocol that is used in the UNIs (user-network interfaces) of the ATM network 5 to interfacing between the personal computer 1-1-1 and the ATM/1394 bridge 4-1-1, and the ASEL layers 16-3 and 17-3 allow application of the same signaling protocol to interfacing between the ATM/1394 bridge 4-2-1 and the personal computer 1-2-1.
A description will now be made of the ASEL (ATM over IEEE 1394 serial bus emulation layer) layer for emulating an AAL5 (ATM adaptation layer type 5)/ATM layer (ITU-T I.363/ITU-T I.361) on the IEEE 1394 link layer of each of the ATM/1394 bridges 4-1-1 to 4-1-m and 4-2-1 to 4-2-n and the personal computers 1-1-1 to 1-1-m and 1-2-1 to 1-2-n.
The ASEL conceals the IEEE 1394 serial bus from software of the apparatus concerned above the ASEL and emulates AAL and ATM layers. Therefore, in an apparatus incorporating the ASEL, multiplexing and demultiplexing on the same UNI with a plurality of VPCs (virtual path connections)/VCCs (virtual channel connections) in an ATM communication are enabled in its own IEEE 1394 serial bus interface. Further, network access protocol software that is compatible with the ATM network 5 and various kinds of application software can be used as they are.
FIG. 3 is a layer relationship diagram showing the position of the ASEL. As shown in FIG. 3, the ASEL provides, as a primitive (transmission/reception information for a communication between layers) for the upper layer, a primitive that is similar to ones provided by various AALs. That is, the ASEL receives AAL_UNITDATA.req (request) from the upper layer and supplies it with AAL_UNITDATA.ind (indicate). The ASEL receives AAL_U_ABORT.req from the upper layer and supplies it with AAL_U_ABORT.ind. Further, the ASEL supplies the upper layer with AAL_P_ABORT.ind. In this manner, software of the upper layer of the ASEL behaves in the same manner as in a case where its lower layer is an AAL.
The ASEL uses, as a primitive for the lower layer, a primitive itself that is provided by the IEEE 1394 link layer. That is, the ASEL supplies the lower layer with LK_ISO_CONT.req and receives LK.CYCLE.ind from it. The ASEL supplies the lower layer with LK_ISO.req and receives LK_ISO.ind from it. Further, the ASEL supplies the lower layer with LK_DATA.req and receives LK_DATA.conf and LK_DATA.ind from it, and supplies the lower layer with LK_DATA.resp.
Further, the ASEL exchanges, with its own (local) ASEL layer management entity (peer interface), an ASEL management primitive including various kinds of management information relating to configuration, faults, performance, alarming, etc. of a counterpart ASEL entity and the ASEL entity itself. For example, when an abnormality has been detected, prescribed management information is supplied to the peer interface and output to the counterpart ASEL entity via a system interface. Control information coming from another ASEL entity is supplied to the ASEL via the system interface and the peer interface.
Next, the main functions of the ASEL will be described. The ASEL entity can set a plurality of VPCs/VCCs on an isochronous channel. The ASEL entity of each of the ATM/1394 bridges 4-1-1 to 4-1-m and 4-2-1 to 4-2-n assigns arbitrary VPI (virtual path identifier)/VCI (virtual channel identifier) values to VPCs/VCCs on isochronous channels that are used by the personal computers 1-1-1 to 1-1-m and 1-2-1 to 1-2-n that are connected to the IEEE 1394 serial bus interface that is accommodated by the ASEL entity itself via the IEEE 1394 serial buses 2-1 to 2-m and 7-1 to 7-n.
Further, the ASEL entity of each of the ATM/1394 bridges 4-1-1 to 4-1-m assigns arbitrary VPI/VCI values to respective self-IDs (e.g., IDs that are automatically assigned according to the IEEE 1394 standard at the time of power application or the like) that are used as counterpart node ID numbers by the personal computers 1-1-1 to 1-1-m that are connected to the IEEE 1394 serial bus interface that is accommodated by the ASEL entity itself via the IEEE 1394 serial buses 2-1 to 2-m. The ASEL entity of each of the ATM/1394 bridges 4-2-1 to 4-2-m assigns arbitrary VPI/VCI values to self-IDs that are used as counterpart node ID numbers by the personal computers 1-2-1 to 1-2-n that are connected to the IEEE 1394 serial bus interface that is accommodated by the ASEL entity itself via the IEEE 1394 serial buses 7-1 to 7-n. The ASEL entity sets and identifies a plurality of VPI/VCI values for respective Dest (destination)-IDs that are counterpart node ID numbers at the time of transmission and for respective Src (source)-IDs that are node ID numbers of the ASEL entity itself at the time of reception. Various parameters relating to a VPC/VCC are set by using a primitive that is supplied to the ASEL layer management via the system interface.
Further, the ASEL assures Qos (quality of service). That is, the ASEL assures, to users, Qos by performing a CBR (constant bit rate) service of the ATM by using IEEE 1394 isochronous packets and by performing a UBR (unassigned bit rate) service and an ABR (available bit rate) service of ATM by using IEEE 1394 isochronous packets.
Next, a connection control procedure for transferring digital video data from the digital video camera 3-1 to the digital video cassette recorder 8-1 will be described with reference to a flowchart of FIG. 4. It is assumed that the personal computers (PCs) 1-1-1 and 1-2-1 perform connection controls in place of the digital video camera 3-1 and the digital video cassette recorder 8-1, respectively.
At step S11, to perform an exclusion control of connection setting, the personal computer 1-1-1 transmits, to the personal computer 1-2-1 that is connected to the same IEEE 1394 serial bus 7-1 as the counterpart digital video cassette recorder 8-1 is connected, a request for accepting connection to the digital video cassette recorder 8-1. This operation can be performed in the manner as described in Japanese Patent Application No. Hei. 8-82545 (corresponding to PCT Application No. JP 97/01178 and U.S. patent application Ser. No. 08/973,175), for example, of the present assignee.
At step S12, after recognizing a node unique identifier (node unique identifiers are assigned in advance to all devices that use the IEEE high-speed serial buses) of the digital video cassette recorder 8-1, the personal computer 1-2-1 starts an exclusion control for other connection acceptance requests and turns on a proxy signaling flag indicating that the personal computer 1-2-1 will execute an ATM signaling process in place of the digital video cassette recorder 8-1. At step S13, the personal computer 1-2-1 transmits, to the personal computer 1-1-1, a response indicating acceptance of connection to the digital video cassette recorder 8-1.
At step S14, the personal computer 1-1-1 turns on a proxy signaling flag indicating that the personal computer 1-1-1 will execute an ATM signaling process in place of the digital video camera 3-1 and starts execution of the ATM signaling process. At step S15, the personal computer 1-1-1 transmits a VCC setting request message to the personal computer 1-2-1. The personal computer 1-1-1 specifies, in the VCC setting request message, that digital video data using CIP is to flow through the connection.
Upon reception of the VCC setting request, at step S16 the personal computer 1-2-1 sets, in its own ASEL entity, VCC parameters such as a VPI/VCI, a Qos type parameter (in this case, CBR (constant bit rate)), an AAL type parameter (in this case, AAL5), an isochronous packet encapsulation method parameter (in this case, CIP format), and a transmission/reception bandwidth parameter. Since the preset proxy signaling flag is on, the transmission/reception bandwidth parameter is set at xe2x80x9c0xe2x80x9d to prevent reception of digital video data that flows through the VCC.
At step S17, the personal computer 1-2-1 transmits an IsoReq message that is an ASEL-CMP (connection management protocol) to the ATM/1394 bridge 4-2-1 as an isochronous resource manager of the IEEE 1394 serial bus 7-1 and thereby requests assigning of an isochronous channel corresponding to the VPI/VCI assigned to the VCC.
Since the ASEL entity of the personal computer 1-2-1 set at step S16 the VCC isochronous packet encapsulation method parameter indicating the CIP format, at step S17 the personal computer 1-2-1 can transmit, to the ATM/1394 bridge 4-2-1, an IsoReq message in which optional mode information is set to a value corresponding to it (i.e., the two MSB-side bits are set at xe2x80x9c01xe2x80x9d and the remaining six bits are set at xe2x80x9c000000xe2x80x9d in the case of DVCR and at xe2x80x9c100000xe2x80x9d in the case of MPEG). By receiving this IsoReq message, the ATM/1394 bridge 4-2-1 similarly recognizes that the VCC isochronous packet encapsulation method is the CIP format.
At step S18, the ATM/1394 bridge 4-2-1 acquires an isochronous channel on the IEEE 1394 serial bus 7-1 and transmits an IsoRply message to the personal computer 1-2-1. At this time, the ASEL entity of the ATM/1394 bridge 4-2-1 registers, in the IsoRply, the VPI/VCI of the VCC and the acquired isochronous channel in such a manner that they are correlated with each other one to one.
At step S19, the personal computer 1-2-1 requests the digital video cassette recorder 8-1 to rewrite the contents of an iPCR (input plug control register) to enable reception on the acquired isochronous channel.
At step S20, the digital video cassette recorder 81 sets the isochronous channel in the iPCR. At step S21, the digital video cassette recorder 8-1 transmits, to the personal computer 1-2-1, a response to the effect that the isochronous channel has been set in the iPCR.
At step S22, the personal computer 1-2-1 transmits a VCC setting response message to the personal computer 1-1-1. At step S23, the personal computer 1-2-1 cancels the exclusion control for other connection acceptance requests and turns off the proxy signaling flag indicating that the personal computer 1-1-1 executes the ATM signaling process in place of the digital video cassette recorder 8-1.
Upon reception of the VCC setting response message, at step S24 the personal computer 1-1-1 sets, in its own ASEL entity, VCC parameters such as a VPI/VCI, a Qos type parameter (in this case, CBR), an AAL type parameter (in this case, AAL5), an isochronous packet encapsulation method parameter (in this case, CIP format), and a transmission/reception bandwidth parameter. Since the preset proxy signaling flag is on, the transmission/reception bandwidth parameter is set at xe2x80x9c0xe2x80x9d to prevent reception of digital video data that flows through the VCC.
At step S25, to request assigning of an isochronous channel on the IEEE 1394 serial bus 2-1 corresponding to the VPI/VCI assigned to the VCC, the personal computer 1-1-1 transmits an IsoReq message that is an ASEL-CMP to the ATM/1394 bridge 4-1-1. At step S26, the ATM/1394 bridge 4-1-1 acquires an isochronous channel on the IEEE 1394 serial bus 2-1 and transmits an IsoRply message to the personal computer 1-1-1. At this time, the ASEL entity of the ATM/1394 bridge 4-1-1 registers, in the IsoRply message, the VPI/VCI of the VCC and the isochronous channel in such a manner that they are correlated with each other one to one.
At step S27, the personal computer 1-1-1 turns off the proxy signaling flag indicating that the personal computer 1-1-1 executes the ATM signaling process in place of the digital video camera 3-1.
At step S28, the personal computer 1-1-1 requests the digital video camera 3-1 to rewrite the contents of an oPCR (output plug control register) to enable reception on the acquired isochronous channel. At step S29, the digital video camera 3-1 sets the isochronous channel in the oPCR. At step S30, the digital video camera 3-1 transmits, to the personal computer 1-1-1, a response to the effect that the isochronous channel has been set in the oPCR.
In the above manner, a connection for transfer of digital video data from the digital video camera 3-1 to the digital video cassette recorder 8-1 is established.
In digital AV devices that are connected to the IEEE 1394 serial buses 2-1 to 2-m and 7-1 to 7-n, the software is not very complex and most of applications are implemented by hardware. That is, such digital AV devices are configured so strong that an operation hardly hangs up (i.e., they are hardly rendered non-operational). In contrast, since the personal computers 1-1-1 to 1-1-m and 1-2-1 to 1-2-n incorporate an enormous amount of software that is more complex than in digital AV devices, the possibility of operation hanging-up is not low. Where such personal computers are connected to respective 1394 serial buses, there is great fear that when one digital AV device is added to or removed from the network system the reliability of the entire network system may be lowered.
In conventional network systems, prior to connection setting, information is exchanged between personal computers point to point by using the IP over ATM. In this case, since connections between personal computers are established in mesh form, the number of connections increases as the scale of the network system increases. For example, if there exist N personal computers, the maximum number Np of necessary connections is equal to N(Nxe2x88x921)/2. This results in a problem that the management of the entire network system becomes complex and that at the occurrence of a trouble it is difficult to make an analysis as to what caused the trouble; that is, the system is less resistant to troubles.
The present invention has been made in view of the above circumstances in the art, and an object of the invention is therefore to realize a more reliable network system.
According to a first aspect of the invention, there is provided a communication control apparatus which controls a communication of a network to which a plurality of bridges that interface between a first network and a second network are connected, comprising storage control means for controlling storage of address information of the second network that is assigned to the first network and that is communicated from the bridges; and connection control means for controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control means.
The first network may be IEEE 1394 serial buses and the second network may be an ATM network.
The connection control means may perform connection on the network in place of the devices.
The communication control apparatus may further comprise exclusion processing means for preventing, when two of the devices are to be connected to each other via the network, the two devices from being connected to other devices.
There is provided a communication control method of a communication control apparatus which controls a communication of a network to which a plurality of bridges that interface between a first network and a second network are connected, comprising a storage control step of controlling storage of address information of the second network that is assigned to the first network and that is communicated from the bridges; and a connection control step of controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control step.
There is provided a program storage medium for causing a communication control apparatus which controls a communication of a network to which a plurality of bridges that interface between a first network and a second network are connected, to execute a process comprising a storage control step of controlling storage of address information of the second network that is assigned to the first network and that is communicated from the bridges; and a connection control step of controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control step.
According to a second aspect of the invention, there is provided a communication control apparatus which interfaces between a first network and a second network and controls a communication of a device connected to the first network in cooperation with a second communication control apparatus, comprising assigning means for assigning address information of the second network to a part of the first network connected to the communication control apparatus; and notifying means for notifying the second communication control apparatus of the address information of the second network that was assigned to the part of the first network by the assigning means.
The communication control apparatus may further comprise concealing means for interfacing between the first network and the second network and for concealing the part of the first network from a higher layer; and correlating means for correlating the concealing means with at least one of the part of the first network and a virtual device connected to the part of the first network.
The communication control apparatus may further comprise emulating means for emulating an operation of the concealing means.
The first network may be IEEE 1394 serial buses and the second network may be an ATM network.
There is provided a communication control method of a communication control apparatus which interfaces between a first network and a second network and controls a communication of a device connected to the first network in cooperation with a second communication control apparatus, comprising an assigning step of assigning address information of the second network to a part of the first network connected to the communication control apparatus; and a notifying step of notifying the second communication control apparatus of the address information of the second network that was assigned to the part of the first network by the assigning step.
There is provided a program storage medium for causing a communication control apparatus which interfaces between a first network and a second network and controls a communication of a device connected to the first network in cooperation with a second communication control apparatus, to execute a process comprising an assigning step of assigning address information of the second network to a part of the first network connected to the communication control apparatus; and a notifying step of notifying the second communication control apparatus of the address information of the second network that was assigned to the part of the first network by the assigning step.
According to a third aspect of the invention, there is provided a communication control system comprising a plurality of first apparatuses for interfacing between a first network and a second network, each of the first apparatuses comprising assigning means for assigning address information of the second network to a part of the first network that is connected to the first apparatus; and notifying means for notifying a second apparatus of the address information of the second network that was assigned to the part of the first network by the assigning means; and the second apparatus for controlling a communication in a network between devices connected to the first apparatuses via the first network, the second apparatus comprising storage control means for controlling storage of the address information of the second network that is assigned to the first network and that is communicated from the first apparatuses; and connection control means for controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control means.
There is provided a communication control method of a communication control system comprising a plurality of first apparatuses for interfacing between a first network and a second network and a second apparatus for controlling a communication in a network between devices connected to the first apparatuses via the first network, the communication control method comprising a communication control method of each of the first apparatuses, comprising an assigning step of assigning address information of the second network to a part of the first network that is connected to the first apparatus; and a notifying step of notifying the second apparatus of the address information of the second network that was assigned to the part of the first network by the assigning step; and a communication control method of the second apparatus, comprising a storage control step of controlling storage of the address information of the second network that is assigned to the first network and that is communicated from the first apparatuses; and a connection control step of controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control step.
There is provided a program storage medium for causing each first apparatus and a second apparatus of a communication control system comprising a plurality of first apparatuses for interfacing between a first network and a second network and the second apparatus for controlling a communication in a network between devices connected to the first apparatuses via the first network, to execute a first process and a second process, respectively, the first process comprising an assigning step of assigning address information of the second network to a part of the first network that is connected to the first apparatus; and a notifying step of notifying the second apparatus of the address information of the second network that was assigned to the part of the first network by the assigning step, the second process comprising a storage control step of controlling storage of the address information of the second network that is assigned to the first network and that is communicated from the first apparatuses; and a connection control step of controlling a connection, via the first network and the second network, between devices connected to the first network by using the address information of the first network that was stored based on the control of the storage control step.
In the communication control apparatus, the communication control method, and the program storage medium according to the first aspect of the invention, address information of the second network is assigned to the first network that is connected to the bridges and a connection via the first network and the second network is controlled by using the address information.
In the communication control apparatus, the communication control method, and the program storage medium according to the second aspect of the invention, address information of the second network that is assigned to the first network is communicated to another communication control apparatus.
In the communication control system, the communication control method, and the program storage medium according to the third aspect of the invention, the first apparatuses assign address information of the second network to the first network and the second apparatus controls a connection via the first network and the second network by using the address information of the second network that has been assigned to the first network.